Rapid in vitro Clonal Propagation of Herbal Spice, Mentha piperita L. Using Shoot Tip and Nodal Explants

A high frequency efficient protocol for rapid propagation of the herbal spice Mentha piperita L. from shoot tip and nodal explants was established by using full and half strength of Murashige and Skoog (MS) medium supplemented with various concentrations of 6-benzyl amino purine (BAP; 1.0-5.0 mg/L) and kinetin (Kn; 1.0-5.0 mg/L). The highest number of shoots (42.0) with 100% frequency was obtained from nodal explants in the full strength of medium containing 3.0 mg/L BAP. For further elongation, microshoots were transferred to MS medium containing different concentrations of gibberellic acid (GA3; 0.5-2.0 mg/L). The highest shoot length (13.1 cm) with 100% frequency was achieved on medium containing 1.0 mg/L GA3. In vitro proliferated shoots were then excised from the shoot clumps and transferred to the rooting medium containing different concentrations of indole butyric acid (IBA; 0.5-2.0 mg/L) and indole acetic acid (IAA; 0.5-2.0 mg/L) alone. Among these, the highest root proliferation was obtained in the medium containing 1.5 mg/L IBA. The rooted plantlets were hardened on MS basal liquid medium and subsequently in polycups containing sterile soil and vermiculite (1:1) and finally transferred to the field. The survival rate was 100% after 25 days.